In recent years, proliferation of a video surveillance system for which cameras, sensors, a storage device, and the like, are installed to prevent occurrence of crimes is significantly proceeding in step with an increase in the number of crimes typified by lock-picking crimes, assailing thieves, arson, and the like. The number of systems that conduct wide-area surveillance of a size of hundreds areas and long-hour recording is also increasing in conjunction with proliferation of IP-based surveillance cameras and a leap in capacity of a storage device. Under such circumstances, a technique for efficiently rooting out a specific person, such as a shoplifter, a stray child, a person who lost property, and the like, has been sought with the aim of lightening a workload for a surveyor.
A related-art technique for rooting out a specific person (a person to be retrieved) at high speed is to store in a database characteristic data (a face, a color, a figure, and the like) pertaining to an indefinite number of persons extracted from respective camera images and to extract from the database a person matching characteristic data on a person to be retrieved and display the extracted person. Patent Document 1 discloses a method for re-performing retrieval operation by making a change to “a countenance, an age, a gender, and the like” on a retrieval screen when a desired person cannot be acquired.